This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Graminaceous plants take up Fe(III) and other transition metals from alkaline soils by secreting phytosiderophores, metal chelators, and then transporting the phytosiderophore-metal complex back across the plasma membrane with YS1 transporters, (Yellow-striped 1). Understanding more about this transporter could lead to an increased source of iron for the under-nourished, iron deficient world. Functional characterization has been performed in Xenopus oocytes. The electrochemical H+ gradient is thought to drive uptake of the phytosiderophore-metal complex. These results have recently been questioned due to the fact that the extracellular acidification used to drive uptake generates a well-characterized artifact in the Xenopus oocytes. We are in the process of expressing the transporters in other heterologous systems, less prone to this artifact, specifically mammalian and insect cell lines for the purpose of characterizing transport. Functional characterization in combination with electrochemical flux measurements will enable identification of the stoichiometry of the transporter.